Design Of Magnetic Actuator Research Articles

Topological optimal design of composite magnetic actuators to improve driving force and thermal conductivity

Topological optimal design of composite magnetic actuators to improve driving force and thermal conductivity

Magnetic Reprogramming of Self‐Assembled Hard‐Magnetic Cilia

AbstractArtificial magnetic cilia are hair‐like structures that can respond to magnetic fields. Using hard magnetic materials in magnetic cilia makes possible programming and reprogramming of the magnetization state and corresponding actuation behaviors. Hard‐magnetic cilia are fabricated through self‐assembly by solvent casting of a slurry of NdFeB microparticles dispersed in a solution of a thermoplastic polyurethane elastomer. These hard‐magnetic cilia are capable of attractive and repulsive responses to magnetic fields, determined by the remanent magnetization of the NdFeB microparticles. An array of cilia can be magnetically reprogrammed through immobilization in ice, applying a damped alternating magnetic field first to reduce the remanent magnetization, and then remagnetizing the cilia with a large field. This demagnetization process significantly improves the reprogrammability of the cilia array. Different responses to magnetic fields can be programmed, including spatially nonuniform behaviors. Reprogrammed hard‐magnetic cilia exhibit unique behaviors in rotating magnetic fields. After reprogramming the magnetization direction along the width of the cilia, rotation and torsion cause them to slowly coil and then quickly uncoil in a snapping behavior. Modeling the magnetic and elastic torques during actuation provides additional insights and aids the design of magnetic cilia actuators based on hard magnets.

One-Coil Long-Stroke Permanent Magnetic Actuator Design Applied to Load Breaker Switch for Railway

This paper proposes a design for a one-coil long-stroke permanent magnet actuator (PMA) applied to a load breaker switch with a novel mechanism applicable to railways. As a new load breaker switch applicable to railway overhead lines has a double-insulation structure of the vacuum interrupter (VI) and a disconnect switch (DS) for higher insulation, the actuator to control the switch requires a very long stroke. While the traditional mechanism of the PMA implements a stroke of 10 to 30 mm, the load breaker switch with a double-insulation structure requires a stroke of 120 mm. To do so, we used the finite element method (FEM) and designed a novel one-coil long-stroke PMA. Then, values from FEM analysis were compared with measured holding force data, and a simplified prototype test-jig was used to confirm the actuator’s operating characteristics. In addition, the electromagnetic force, plunger rotation, and part weight ratio, which affect operating performance, were adapted in its design. By doing so, we confirmed the operating performance required for the one-coil long-stroke PMA for a new load breaker switch with a double-insulation structure with a VI average opening speed of 1.4 m/s and an average closing speed of 0.9 m/s at 1/2 of full stroke.

Design and Control of Magnetic Shape Memory Alloy Actuators.

This paper presents research on the application of magnetic shape memory alloys (MSMAs) in actuator design. MSMAs are a relatively new group of so-called smart materials that are distinguished by repeatable strains up to 6% and dynamics much better than that of thermally activated shape memory alloys (SMAs). The shape change mechanism in MSMAs is based on the rearrangement of martensite cells in the presence of an external magnetic field. In the first part of the article a review of the current state of MSMA actuator design is presented, followed by a description of the design, modelling and control of a newly proposed actuator. The developed actuator works with MSMA samples of 3 × 10 × 32 mm3, guaranteeing an available operating range of up to 1 mm, despite its great deformation range and dynamics. In the paper its dynamics model is proposed and its transfer function is derived. Moreover, the generalised Prandtl-Ishlinskii model of MSMA-actuator hysteresis is proposed. This model is then inverted and used in the control system for hysteresis compensation. A special test stand was designed and built to test the MSMA actuator with compensation. The step responses are recorded, showing that the compensated MSMA actuator exhibits the positioning accuracy as ±2 µm. As a result, the authors decided to apply a control system based on an inverse hysteresis model. The paper concludes with a summary of the research results, with theoretical analysis compared with the registered actuator characteristics.

Evolutionary design of magnetic soft continuum robots

Worldwide cardiovascular diseases such as stroke and heart disease are the leading cause of mortality. While guidewire/catheter-based minimally invasive surgery is used to treat a variety of cardiovascular disorders, existing passive guidewires and catheters suffer from several limitations such as low steerability and vessel access through complex geometry of vasculatures and imaging-related accumulation of radiation to both patients and operating surgeons. To address these limitations, magnetic soft continuum robots (MSCRs) in the form of magnetic field-controllable elastomeric fibers have recently demonstrated enhanced steerability under remotely applied magnetic fields. While the steerability of an MSCR largely relies on its workspace-the set of attainable points by its end effector-existing MSCRs based on embedding permanent magnets or uniformly dispersing magnetic particles in polymer matrices still cannot give optimal workspaces. The design and optimization of MSCRs have been challenging because of the lack of efficient tools. Here, we report a systematic set of model-based evolutionary design, fabrication, and experimental validation of an MSCR with a counterintuitive nonuniform distribution of magnetic particles to achieve an unprecedented workspace. The proposed MSCR design is enabled by integrating a theoretical model and the genetic algorithm. The current work not only achieves the optimal workspace for MSCRs but also provides a powerful tool for the efficient design and optimization of future magnetic soft robots and actuators.

Analysis of vector hysteresis models in comparison to anhysteretic magnetization model

The design of electrical machines and magnetic actuators requires accurate models to represent hysteresis effects in ferromagnetic materials. The magnetic nonlinearity of the iron core is usually considered by an anhysteretic magnetization curve. With this assumption, hysteresis’ effects in the field computation are completely neglected. This paper presents a comparative study of different hysteresis models, particularly Pragmatic Algebraic Model (PAM) and vector stop model, with regard to a vector anhysteretic anisotropic model. The PAM turns out to be an efficient model implemented with one mathematical equation. The multi cells stop model relies on a consistent thermodynamic formulation, whose dissipation corresponds to a dry friction-like element. Both models implement a constitutive relationship, in which the magnetic flux density vector as independent input and magnetic field strength as output. With a rotational single sheet tester (RSST), various tests for a sample of material FeSi24-50A (FeSi) with a silicon proportion of 2.4 wt% can be proceeded under the application of relevant field distribution. The obtained measured data are applied to parameterize and validate the models. Following numerical experiments the results are compared with those obtained by means of an anhysteretic anisotropic model.

Magnetic Actuator Design for Strip Stabilizers in Hot-Dip Galvanizing Lines: Examining Rules and Basic Tradeoffs

Electromagnetic strip stabilizers are viable tools for controlling the shape of steel strips in hot-dip galvanizing lines. These stabilizers usually consist of multiple electromagnets located at the top and bottom sides of the strip. Although the general design of electromagnetic actuators is a well-established field of research, not all of this expertise is utilized in currently installed strip-stabilization systems. This article presents common design tradeoffs and rules for the construction and installation of these electromagnets and aims to assist the development of future strip stabilization systems. The behavior of thin steel strips in the magnetic field of the actuators is studied in detail. These results are extended to the multiactuator setup commonly used in hot-dip galvanizing lines. The negative effects arising from the magnetic coupling between the actuators are discussed, and the means used to prevent these negative effects are presented. Finally, all of the conclusions are validated via force measurements carried out in an industrial hot-dip galvanizing line.

Modeling of history‐dependent magnetization in the finite element method on the example of a postassembly rotor magnetizer

AbstractDemagnetization characteristics of permanent magnets play a central role for the design and optimization process of permanent magnet electrical machines and magnetic actuators. Currently, practical issues, such as loss of performance of electromagnetic energy conversion devices, due to demagnetization effects in permanent magnets or due to reduced servo‐dynamics in magnetic actuators, cannot be addressed by using conventional material models or are investigated by using rough approximations valid in restricted operation regions, if at all. This paper strives to integrate demagnetizing characteristics dependent on previous magnetizing field strength in the finite element method. The discussed examples are a magnetizer of a single permanent magnet and a spoke‐type permanent magnet rotor.

Topology optimization of anisotropic magnetic composites in actuators using homogenization design method

This work presents topology optimization of anisotropic magnetic composites in actuators. The magnetic composite consists of two different ferromagnetic materials with high and low magnetic reluctivity, which correspond to matrix and fiber materials, respectively. The magnetic composite is expected to enhance the actuator performance when it is properly designed. The proposed design optimization scheme can find the composite layout, fiber volume fraction, and fiber orientations to achieve an actuator force maximization. In the proposed scheme, four microstructure design variables are assigned at each finite element, and the effective homogenized material property (i.e., magnetic reluctivity) is calculated using the asymptotic homogenization method. The microstructure design variables are then optimized to achieve the optimal distribution of the homogenized material property in a macroscopic scale. In the design result, discrete fiber orientations and volume fractions are achieved by applying the discrete penalization scheme. In addition, the obtained composite design result is visualized using the projection method proposed for a periodic composite design result. The effectiveness of the proposed topology optimization procedures is validated in magnetic actuator design examples. In addition, the design result of anisotropic composite is compared with the isotropic multi-material design result to validate the benefit of anisotropic composite in actuators.

Self-Assembly Magnetic Chain Unit for Bulk Biomaterial Actuation

Untethered microrobot has been regarded as one of the most powerful tools for performing specific in vitro/vivo tasks, especially magnetic actuated microrobot owing to its biocompatible energy source. However, although numerous design and fabrication technologies of magnetic microrobot have been developed, the improvement of magnetic actuation manner reaches the limit, which mainly relies on the specific structure design (helix) or strong gradient magnetic field to realize locomotion. Inspired from surface cilia dependent paramecium swimming, this letter reports a new self-assembly magnetic actuation concept design for bulk biomaterial motion based on the partial asymmetrical heterofunction of magnetic chain units. Compared with the existing design and fabrication of magnetic microrobot actuators, our proposed self-assembly magnetic chain unit method is succinct, economical, structure unconstrained, and material unconstrained. In this work, the tanglesome bulk fiber fabrication based on flow-focusing microcapillary system is first introduced, which is utilized for structure unconstrained and material unconstrained actuation demonstration. Second, the six degrees of freedom electromagnetic coil system is proposed for presenting the magnetic actuation based on self-assembly magnetic chain units. After that, the self-assembly mechanism and magnetic control mechanism are developed to explain the fabrication and actuation procedure. Finally, the self-assembled magnetic chain units can achieve up to 150 $\mu$ m length during the fabrication process, which can actuate bulk biomaterial with much larger size than itself. The self-assembly magnetic chain unit and actuation experimental results verify the feasibility and practicability of the above-mentioned concepts. This research opens new prospects for magnetic microrobot actuation, which is expected to advance the biomedical area, such as for in vitro/vivo targeted therapy and organ-on-a-chip research.

Multi-Objective Optimization of Magnetic Actuator Design Using Adaptive Weight Determination Scheme

This paper presents a multi-objective topology optimization method for a magnetic actuator design considering both magnetic force and actuator volume. We use a gradient-based optimization algorithm and the multi-objective optimization problem is formulated using a weighted sum of the objective functions. An adaptive weight determination scheme is iteratively employed to update the weighting coefficients of the objective functions to obtain non-dominated solutions. To ensure that the optimal solutions are evenly distributed in the objective domain, e-equality constraints are applied in the empty regions of the non-dominated solutions. The values of the constraints are determined by considering the distance ratios of the objective functions. The optimization problem is formulated to maximize the magnetic force and minimize the volume of the actuator. A level set function is used as a topological design variable to obtain optimal designs that have clear structural boundaries.

Level-Set-Based Topology Optimization Using Remeshing Techniques for Magnetic Actuator Design

This paper proposes a new level-set-based topology optimization method for magnetic actuator design using remeshing techniques that can generate meshes on the exact structural boundaries to improve the accuracy of finite-element analysis. Two remeshing techniques, such as the modified adaptive mesh method and the extended finite-element method (XFEM), are introduced for the optimization process. To control the computational time with meshing that is economical and analysis that is accurate, a new resolution parameter that can manage the level of mesh density around the level-set boundaries is employed in the modified adaptive mesh method. In the XFEM, the enrichment term in the element shape function is employed to track the exact outer boundary of the actuator. The optimization problem is formulated to maximize the magnetic force between the core and an armature under the volume constraint of the ferromagnetic material. To verify the effectiveness of the proposed method, it is applied to an electromagnetic problem for an optimal C-core actuator design that is very sensitive to structural boundaries.

Isogeometric Shape Optimization of Ferromagnetic Materials in Magnetic Actuators

We present an isogeometric shape optimization method for the design of magnetic actuators. The objective is to maximize the magnetic force of actuators, which tends to be highly dependent on the geometry around air gap. The isogeometric shape optimization is known to be robust for the actuator design, since it can preserve the exact geometry during the design optimization. Using the Maxwell stress tensor method, the magnetic force is calculated through the isogeometric analysis. The analytical design sensitivity provides geometric exactness due to the use of non-uniform rational B-splines basis functions. The optimization problem is solved using a gradient-based algorithm of modified method of feasible directions. To demonstrate the robustness of the isogeometric method, the geometric dependence of magnetic forces is investigated. In addition, the isogeometric optimization method is applied to the design problems of linear and rotating actuators, which yields the optimal shape of the ferromagnetic materials around the air gap.

Optimal Design of Permanent Magnetic Actuator for Permanent Magnet Reduction and Dynamic Characteristic Improvement using Response Surface Methodology

Permanent magnetic actuators (P.M.A.s) are widely used to drive medium-voltage-class vacuum circuit breakers (V.C.B.s). In this paper, a method for design optimization of a P.M.A. for V.C.B.s is discussed. An optimal design process employing the response surface method (R.S.M.) is proposed. In order to calculate electromagnetic and mechanical dynamic characteristics, an initial P.M.A. model is subjected to numerical analysis using finite element analysis (F.E.A.), which is validated by comparing the calculated dynamic characteristics of the initial P.M.A. model with no-load test results. Using tables of mixed orthogonal arrays and the R.S.M., the initial P.M.A. model is optimized to minimize the weight of the permanent magnet (P.M.) and to improve the dynamic characteristics. Finally, the dynamic characteristics of the optimally designed P.M.A. are compared to those of the initially designed P.M.A.

A novel magnetic actuator design for active damping of machining tools

Parts and cutting tools with large structural flexibility experience both forced and chatter vibrations during machining, resulting in poor surface finish or damage to the machine. This paper presents the design principles of a novel 3 degrees of freedom linear magnetic actuator which increases the damping and static stiffness of flexible structures during machining. The proposed actuator can deliver 248N force in two radial (x, y) directions and 34N×m (torque) in torsional (θ) direction up to 850Hz. The force and torque reduces to 107N and 14.5N×m at 2000Hz, hence it can actively damp a wide range of structural modes. The magnetic force is linearized with respect to the input current using magnetic configuration design strategy. Loop shaping controllers are designed for active damping of boring bar vibrations. The static and dynamic stiffnesses of the boring bar were considerably increased with the designed actuator, leading to a significant increase in chatter-free material removal rates during cutting tests.

Design and Optimization of Magnetic Levitation Actuators for Active Vibration Isolation System

Actuator based on Lorentz force exhibits excellent isolating performance with its non-contact characteristic, especially during frequency bandwidth below 5Hz. In this paper, mathematical model of the magnetic levitation actuator is constructed. In order to obtain better performance, parametric design of the structure of magnetic actuator is carried out and a multi-objective optimization method is proposed to maximize Lorentz force and minimize the mass of coil on the basis of genetic algorithm in the optimization process. A designing optimization program is developed, by which optimized parameters of magnetic actuator with maximal actuator force and minimal mass of coil can be identified to conduct experiment on ground. Compared with initial values in an instance, the optimized method is proven to be feasible and has the value of practical application.

Characteristic analysis and design of a novel permanent magnetic actuator for a vacuum circuit breaker

In this study, a novel permanent magnetic actuator (PMA) termed a separated permanent magnetic actuator (SPMA) is proposed. The efficiency of the proposed SPMA is significantly higher than a conventional PMA because of its innovative structure, with which the magnetic flux path is efficient and the holding forces can be designed independently taking the unique values of each load into consideration. Hence, the SPMA is smaller in size and lower in cost than the conventional PMA. For the SPMA, a characteristic analysis and design method using a two-dimensional finite element method, an equivalent circuit, an equation of motion and a time difference method is suggested in this study to save time and reduce the costs incurred because of the experimental trial and error deign. The SPMA was designed and prototyped such that the usefulness of the SPMA for application to a vacuum circuit breaker and the reasonableness of the suggested characteristic analysis and design method were confirmed by the experimental data.

Structural Optimization of a Multi-Physics Problem Considering Thermal and Magnetic Effects

Most researches regarding structural design of electromagnetic systems have been focused on a single physical phenomenon such as magnetic, electric or thermal effect. However, analysis and design of the multi-physics phenomenon is coming to the fore related with the actuator system targeting on the small size and high performance. Two or more physics phenomena are taken into account in a multi-physics system and the multi-physics analysis is performed using the governing equation in the formulation of a partial differential equation. Accordingly, in actuator design, it is generally hard to predict an optimal shape accurately considering both the magnetic and the thermal effect simultaneously. The objective of this research is set to establish a simultaneous/parallel design process for a multi-physics problem combining magnetic and thermal effects by employing the adoptive weighting factor while the previous work mostly suggests a sequential design process. The proposed method has been applied to yoke shape design of a C-core type magnetic actuator for minimizing the heat transfer effect as well as maximizing the actuating force. The topology optimization scheme based on the density approach is employed to obtain the optimal shape.

Analysis of a complete model of rotating machinery excited by magnetic actuator system

Rotating machines have a wide range of application involving shafts rotating at high speeds that must have high confidence levels of operation. Therefore, the dynamic behavior analysis of such rotating systems is required to establish operational patterns of the equipment, providing the basis for controller development in order to reduce vibrations or even to control oil instabilities in lubricated bearings. A classical technique applied in parameter identification of machines and structures is the modal analysis, which consists of applying a perturbation force into the system and then to measure its response. However, there are mainly two problems in modal analysis concerning the excitation of rotating systems. First, there are limitations to the excitation of systems with rotating shafts when using impact hammers or shakers, due to friction, undesired tangential forces, and noise that can be introduced in the system response. The second problem relies in the difficulty of exciting backward whirl modes, an inherent characteristic from these systems. Therefore, the study of a non-contact technique of external excitation, also capable of exciting backward whirl modes, becomes of high interest. In this sense, this article deals with the study and modeling of a magnetic actuator, used as an external excitation source for a rotating machine, mainly in backward whirl mode. Special attention is given to the actuator model and its interaction with the rotor system. Differently from previous works with similar proposal, which uses current and air gap measurements, here the external excitation force control is based on the magnetic field directly measured by hall sensor positioned in the pole center of the magnetic actuator core. The magnetic actuator design was completely developed for this purpose, opening different paths to experimental application of this device, for example, fault detection analysis based on directional modes. It is also presented a comparison between the numerical simulations and practical tests obtained from a rotor test rig and an experimental evidence of the backward whirl was accomplished based on the numerical simulation results.

Topology Optimization of a Magnetic Actuator Based on a Level Set and Phase-Field Approach

This paper aims to develop a topology optimization method for magnetic actuator design, which can control the geometrical complexity of optimal configurations, using a level set model that incorporates a fictitious interface energy model based on concepts in the phase-field method. By adding a fictitious interface energy term to the objective functional, the optimization problem is sufficiently relaxed and the obtained optimal configurations have sufficient smoothness. The optimization problem is formulated to maximize the performance of a magnetic actuator under a volume constraint for the ferromagnetic material. The update scheme for implicit moving boundaries is developed based on time evolutional equations. The proposed method is applied to the structural design of a C-core actuator and a numerical example confirms the effectiveness of the method for achieving optimal configurations that deliver enhanced performance.